In response to rapidly increasing demand for a wide variety of telecommunication services, high speed, large capacity digital packet switching networks have been proposed. To meet these demands in an efficient and cost effective manner, a single packet network must be able to handle simultaneously different kinds of telecommunication services which have conflicting requirements. Moreover, these services must be accommodated in a manner which constitutes an effective and efficient use of available communication resources.
The proposed packet switching networks must be capable of handling real time services such as voice, video, and smoothly transmitted data transmissions without significant degrees of delay or jitter. These types of transmissions have short term (peak) bandwidth requirements which are substantially the same as their long term (average) bandwidth requirements. These transmissions are most conveniently handled by allocation of their bandwidth requirements in the network for the entire duration of those transmissions along the entire call routing path from the transmitter to the receiver.
Certain bursty data transmissions, on the other hand, do not have strong jitter or delay requirements. These kinds of transmissions, however, may involve periods of high rates of data transmission with long periods of little or no data transmission. For such transmissions, the short term (peak) bandwidth requirements can be very high compared to the long term (average) bandwidth requirements. Allocation of peak bandwidth, as in the case of real time services mentioned above, would be an inefficient use of the network, and is not necessary, for such bursty data transmissions not having stringent delay or jitter requirements. Although bursty data transmissions may not have strong jitter or delay requirements, they do have stringent loss requirements. Specifically, it is particularly important to keep the probability of packet loss very small. If such probability is not kept very small, the resulting packet retransmissions that are needed to complete the transmission can overwhelm the network and cause congestion collapse, particularly in high speed networks carrying a large amount of communication activity in which the amount of data in the network can increase dramatically with trunk speed.
Accordingly, there is a need for an effective congestion avoidance scheme, particularly, for very bursty data transmissions, which keeps the probability of packet loss very small. Furthermore, there is a need for such a congestion avoidance scheme which is compatible with congestion avoidance schemes used for real time transmissions and which is not wasteful of communications resources.